Determining the Void Fraction in the Hydraulic Design of Geothermal Steam-Water Mixture Piping

A. N. Shulyupin; N. N. Varlamova

摘要

Abstract Taking into account new problems arising in the transportation of a steam-water heat carrier to support operation of geothermal power plants (GeoPP), a procedure is outlined for determining the void fraction considering the gravity component of the pressure drop in the hydraulic design calculations of steam-water piping. Unavailability of data on the void fraction under the conditions of geothermal heat carrier transportation is noted. The drift flux model determining the steam velocity averaged over the channel cross-section was used to solve the formulated problem for upward flows. The factors affecting the distribution parameter and the drift velocity are reviewed. It is noted that the drift velocity depends not only on the gravity force but also on the hydrodynamic effect, which can be taken into account using the advanced distribution parameter. A similar approach has been proposed for downward flows according to which the liquid phase velocity averaged over the channel cross-section is calculated using equivalents of the empirical coefficients determined from the condition of equality of the parameters calculated for the upward and downward flows as applicable to the horizontal flow. The empirical values included in the recommended calculation formulas have been established. The proposed recommendations have been used in developing a computer code for the hydraulic design of pipelines. In addition to the gravitational pressure drop, the code also calculates the pressure drop due to friction or local resistance using formulas, which offers good agreement with the experimental data. To verify the model used in the program for the calculation of the gravitational pressure drop, the predictions were compared with the experimental data of the pressure drop across the pipeline from the Geo-1 well to the Verkhne-Mutnovskaya GeoPP (Kamchatka), which is in operation and features the maximum height difference among all existing domestic pipelines carrying steam-water mixture. A good agreement was found between the predictions and the experimental data on pressure drops, which indirectly confirms the adequacy of the recommended procedure for determining the void fraction.

机译：摘要针对地热电厂（GeoPP）在水汽热载体运输中出现的新问题，提出了在汽水管道水力设计计算中考虑压降重力分量的空隙率确定程序。注意到在地热热载体运输条件下空隙部分的数据不可用。使用确定通道横截面平均蒸汽速度的漂移通量模型来求解上行流的公式化问题。综述了影响分布参数和漂移速度的因素。值得注意的是，漂移速度不仅取决于重力，还取决于流体动力学效应，这可以使用高级分布参数来考虑。对于向动，已经提出了一种类似的方法，根据该方法，使用经验系数的等价物计算通道横截面上的平均液相速度，该经验系数是根据适用于水平流动的向上和向动计算的参数相等条件确定的。已经建立了推荐计算公式中包含的经验值。所提出的建议已被用于开发用于管道水力设计的计算机代码。除了重力压降外，该代码还使用公式计算了由于摩擦或局部阻力引起的压降，这与实验数据非常吻合。为了验证程序中用于计算重力压降的模型，将预测结果与从Geo-1井到Verkhne-Mutnovskaya GeoPP（堪察加半岛）的管道压降的实验数据进行了比较，该管道正在运行中，其高度差是所有现有国内所有输送蒸汽水混合物的管道中最大的。在压降的预测和实验数据之间发现了很好的一致性，这间接证实了确定空隙分数的推荐程序的充分性。

Determining the Void Fraction in the Hydraulic Design of Geothermal Steam-Water Mixture Piping

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